May be a new version of the canon 35 or 135L. They are of the oldest lens.
A lot of lenses are even older : the 50mm f2.5 Compact Macro and 135mm f2.8 Soft Focus (1987), 50 f1.8 II (1990), 100 f2, 45mm and 90mm TS-E (1991), 20mm f2.8 and 85 f1.8 (1992), 50mm f1.4 and 400mm f5.6 (1993) and 28mm f1.8 (1995).
The 35mm f1.4 would nevertheless need a refresh (improved IQ and weather sealing), the 135mm f2 could use weather sealing and IS, as well as the 400mm f5.6.
I am more thinking of 45mm and 90mm TS-E (100mm f3.5 L
Macro TS-E) and wide zooms (14-24mm and 16-50mm IS).
I would love to see a 180mm Macro II, sealed and stabilised, but I doubt it will happen.